1. Field of the Invention
The present invention related to a system for detecting a vibration displacement by means of using a detecting assembly composed of a piezoelectric substrate and input- and output interdigital transducers.
2. Description of the Prior Art
Conventional devices for detecting a vibration displacement are classified into two types. One is touch type, and the other is untouch type. Devices as an electric micrometer for measuring a minute displacement, a digital gauge for a small displacement, a rotary encoder for a rotation displacement, and a linear scale for a large displacement belong to the touch type. The rotary encoder is used for controlling a rotation velocity or a rotation frequency of a rotatory thing. The electric micrometer, the digital gauge or the linear scale is used as a reference for measuring the length of a thing, or used for inspection of machine. These touch type devices have some problems on measurement accuracy, response time, difficulty in use, durability and manufacturing. Devices as a laser-type sensor and an electroacoustic-type sensor belong to the untouch type. The laser-type sensor including a semiconductor position-sensing device is mainly used for measuring a vibration displacement along the direction vertical to the laser beam applied to a thing. The laser-type sensor has a defect that the longer the length of the laser beam, the lower the measurement accuracy because of flickering of the laser beam itself. In addition, the use of the laser-type sensor is impossible for the measurement in opaque media. The electroacoustic-type sensor is used for measuring the vibration displacement in a thing near a terminal of a pipe. The electroacoustic-type sensor has some problems on measurement accuracy, resistance for a change of circumstances, and so on.